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This paper describes the synthesis and evaluation of a series of multifunctional poly-l-glutamic acid derivatives that can be used as vectors for gene delivery. They readily form polyelectrolyte complexes with DNA, resulting in a reduced surface charge and size of the DNA. The formation of a polymer-DNA complex and the stability toward serum albumin was analyzed by ethidium bromide fluorescence measurements and agarose gel retardation studies. Most polymers, except those with more than 80% imidazoles, are able to condense calf thymus DNA, thus forming complexes with sizes varying between 105 and 172 nm. The surface charge of the complexes was determined at different charge ratios by zeta potential measurements. The buffering properties of the polymers were determined via titration studies. The results show that the polymers are able to buffer the endosomal environment, although to a smaller extent than polyethyleneimine. The first part of this study is devoted to the synthesis and the physicochemical evaluation of the multifunctional polymers and their use as carriers for genetic information. The second part, to be published subsequently, discusses the biological evaluation of the polymers and their complexes with DNA.

Cationic polymers, such as poly-l-lysine (pLL) and polyethyleneimine (pEI), are receiving growing attention as vectors for gene therapy. They form polyelectrolyte complexes with DNA, resulting in a reduced size of the DNA and an enhanced stability toward nucleases. The major disadvantages of using both polymers for in vivo purposes are their cytotoxicity and, in the case of pEI, the fact that it's not biodegradable. In this work, we investigated the interaction between a series of cationic, glutamic acid based polymers and red blood cells. The MTT test was used to investigate the cytotoxicity of the complexes. The ability of the polymers to stabilize DNA toward nucleases was investigated. Transfection studies were carried out on Cos-1 cells. The results from the haemolysis studies, the haemagglutination studies, and the MTT assay show that the polymers are substantially less toxic than pLL and pEI. The polymers are able to protect the DNA from digestion by DNase I. The transfection studies show that the polymer-DNA complexes are capable of transfecting cells, most of them with poor efficiency compared to pEI-DNA complexes.

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